1. Field of the Invention
The present invention generally relates to diagnostic instruments for human and veterinary applications, and more specifically relates to methods and systems for calibrating such instruments.
2. Description of the Prior Art
Diagnostic instruments have been used for decades in both the human and veterinary markets. These instruments include hematology analyzers, blood chemistry analyzers and other instruments that determine certain physiological properties of patients. In the veterinary market, the VetTest® chemistry analyzer and the VetAutoread™ automated hematology analyzer have been available since at least the 1990's. Some analyzers, like the VetAutoread™ hematology analyzer manufactured by IDEXX Laboratories, Inc. of Westbrook, Me., (see, www.idexx.com), utilize a fixed optical reference to determine instrument performance. Other analyzers, like the IDEXX LaserCyte® hematology analyzer, incorporate polymers with fixed size and index of refraction to ensure optical performance referred to as Qualibeads™. In addition, some analyzers, like the Sysmex XT-V manufactured by Sysmex Corp. of Hyogo, Japan, (see, www.sysmex.com), utilize a fixed cell control material to ensure assay performance. The veterinary market is very cost sensitive and controls are not run in the same manner as in human practices, which generally run fixed cell controls approximately at least once per 8-hour shift. In addition, for veterinary applications, species specific concerns arise since each species may have a different response to the system chemistry and different algorithms are often employed by species. Therefore, alternative methods are required to ensure instrument performance.
Patient-based approaches have been proposed, such as described in the aforementioned pending U.S. patent application Ser. No. 12/932,192, that provide a means to trend patient data in batches to reduce the impact of individual patient responses. The batches can then be evaluated in a control chart utilizing control chart rules to determine if the system has moved out of control. Fuzzy Logic approaches can then be used to define system optimization adjustments that bring the system back into control. This approach has the inherent benefit that the analyses are performed with patient data on a species-specific basis. This approach can run into difficulties if there are external factors that cause system shifts, such as reagent lot changes. Alternative approaches are required to handle patient sample data sets that are convoluted with reagent lot variability.